1. Field of the Invention
The present inventions pertain to semiconductor fabrication processing. More particularly, the present inventions relate to a system the quick removal of residue slurry and/or stagnate slurry chemical from the polishing pad during CMP processing of the wafer to control the removal rate of the substrate.
2. Description of the Prior Art
Referring now to FIGS. 1A-2, there is shown a partial perspective view of a prior art CMP machine 100 and a side partial perspective view of a wafer 105 (FIG. 2). The CMP machine 100 is fed wafers to be polished. The CMP machine 100 picks up the wafers with an arm 101 and places them onto a rotating polishing pad 102. The polishing pad 102 is made of a resilient material and is textured, often with a plurality of predetermined groves, to aid the polishing process. The polishing pad 102 rotates on a platen 104, or turn table located beneath the polishing pad 102, at a predetermined speed, usually from 30 up to 60 RPMs. A wafer is held in place on the polishing pad 102 and the arm 101 by a carrier ring and a carrier film not shown. The lower surface of the wafer 105 rests against the polishing pad 102. The upper surface of the wafer 105 is against the lower surface of the carrier film of the arm 101. As the polishing pad 102 rotates, the arm 101 rotates the wafer 105 at a predetermined rate. The arm 101 forces the wafer 105 into the polishing pad 102 with a predetermined amount of down force. The CMP machine 100 also includes a slurry dispense tube 107, extending across the radius of the polishing pad 102. The slurry dispense tube 107 dispenses a flow of slurry 106 onto the polishing pad 102.
The slurry 106 is a mixture of deionized water and polishing agents designed to aid chemically the smooth and predictable planarization of the wafer. The rotating action of both the polishing pad 102 and the wafer 105, in conjunction with the polishing action of the slurry, combine to planarize, or polish, the wafer 105 at some nominal rate. The polishing action of the slurry is comprised of an abrasive frictional component and a chemical component. The abrasive frictional component is due to the friction between the surface of the polishing pad, the surface of the wafer, and abrasive particles suspended in the slurry. The chemical component is due to the presence in the slurry of polishing agents which chemically interact with the material of the dielectric or metal layer of the wafer. The chemical component of the slurry is used to soften the surface of the dielectric layer to be polished, while the frictional component removes material from the surface of the wafer.
Slurry dispense termination is accomplished by turning off a pump, which will stop the flow of slurry onto the pad. After the slurry dispense process is terminated, the wafer substrate is still exposed to the slurry and pad. The residue slurry which was dispensed on the pad will remain on the pad and continue reacting with the wafer substrate. This will result in a non-uniform removal of the wafer substrate due to stagnate slurry on the pad. The standard removal process has a low flow stream of water is dispensed from water dispense tube 108 onto the pad, which does not remove the slurry completely and quickly from the surface of the pad. The wafer substrate is then rid of the slurry.
What is needed is a method and/or apparatus which will quickly remove the slurry from the pad, thus more accurately controlling the removal rate of the substrate.
This object, and others, is satisfied by Applicant""s present inventions disclosed herebelow.
One embodiment of the present inventions relates to a method for clearing slurry from a polishing pad in a CMP process including placing a wafer substrate in contact with a polishing pad while rotating the polishing pad at a first speed. Slurry is dispensed onto the polishing pad while the pad is rotating at the first speed. After slurry dispense has terminated, a high pressure fluid is sprayed around the wafer substrates to remove slurry from between the wafer substrates and the polishing pad. The pad is rotated at a greater speed while the high pressure fluid is sprayed.
In another embodiment of the present inventions, a slurry dispense bar including a high pressure spray portion and a slurry dispense portion located over the polishing pad is provided, wherein the high pressure fluid is sprayed around said wafer substrates to remove slurry from between said wafer substrates and the pad using the high pressure spray portion of said slurry dispense bar.
Related objects and advantages of the present invention will be apparent from the following description.